https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119923
Bug ID: 119923
Summary: `-pedantic-errors` should imply `-fno-ms-extensions`
on MinGW
Product: gcc
Version: 14.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: iamsupermouse at mail dot ru
Target Milestone: ---
GCC on Windows has a relatively little-known flag `-fno-ms-extensions`, which
disables some problematic MSVC-like extensions, which aren't otherwise disabled
even by `-std=c++?? -pedantic-errors`.
Here are two examples of things `g++ -std=c++26 -pedantic-errors` allows on
MinGW, and that `-fno-ms-extensions` rejects:
template <typename T>
foo() {return 42;} // Missing return type.
struct A {void blah() {}};
auto ptr = A::blah; // Missing `&`.
I suggest that `-fno-ms-extensions` should be enabled by default if
`-pedantic-errors` is used.
For comparison, Clang in MinGW mode doesn't allow neither of those, and I
couldn't find any flag to enable them. I've been using it for some time, and
those missing extensions never came up as an issue.
Clang ignores `-f[no-]ms-extensions` in MinGW mode entirely. In MSVC-compatible
mode this flag is harmful, as it disables `__declspec(dllexport)` and friends,
unless enabled separately via `-fdeclspec`.
